Hi adamgeorge, great question. First off, since it looks like you're based in the UK, there may be some parts of what I mention below that doesn't apply. Usually, Microsoft keeps things pretty standard, but compliance with per country regulations is definitely a thing. Anyways!

OVS (Open Value Subscription) is considered a committed, or company-wide volume licensing program. In this program:

"In a company wide agreement an organization must license one Desktop Platform Product for every Qualified Device."

Based on the product SKU (2UJ-00008), this is the Education Enterprise CAL, this is considered a desktop platform product. However, if you also have another Desktop Platform Product active, this SKU & the others count towards hitting that goal.

e.g. You have 100 Qualifying Devices. 50x have Windows 10 Enterprise, 50x have Office 2019 Professional Plus. This is in compliance(Windows 10 Enteprise and Office 2019 Professional Plus are both considered Desktop Platform Products.)

Qualifying devices are described as:1) Personal desktop computers, portable computers, workstations or similar devices capable of running Windows 10 Pro locally, or2) Any device that is used to access a Virtual Desktop Infrastructure

Devices not managed by the organization are excluded from this.

For the Anniversary payments:"Each anniversary the organization pays for L&SA for the total number of PCs regardless of whether that number has increased (true up) or decreased (true down), provided the number of PCs does not drop below 5, which is the program minimum."

Also, I'd confirm everything based on the Microsoft Product Use Rights doc. Here is the UK version.

TL;DR - You have to get a license for every desktop/laptop you have, but other SKUs do count beyond the one you linked.